Atambayev went on a medical leave after suffering chest pains on a flight last month and undergoing an examination in Turkey.

His illness followed a public row with several former political allies who oppose his constitutional reform plan.

The ruling coalition led by Atambayev’s Social Democratic party has nevertheless pressed ahead with the plan and this week passed the first reading of a bill calling a referendum on the reforms on Dec.4.

The changes would strengthen the powers of the prime minister, a role which Atambayev could in theory take on after stepping down as president, although he said in August he had no such plan.

Kyrgyzstan, an impoverished, mostly Muslim former Soviet republic of 6 million, has been politically volatile for more than a decade. Violent protests in 2005 and 2010 toppled two successive presidents.